The present invention relates to a three-dimensional fabric, useful in particular in parietal and/or visceral surgery, but also able to be applied in other areas of surgery.
The present invention will be described more particularly with respect to a prosthetic fabric of said type, intended to be used for the repair of hernias or eventrations.
For a long time, surgeons have used flat prosthetic fabrics, that is to say two-dimensional, for repairing or replacing any part of the body, such as an aponeurosis, or a muscular wall, destroyed or damaged, for example as a result of a traumatism. Consequently, there are at present a very large number of such prosthetic fabrics, manufactured or obtained using various processes, for example weaving, knitting, or moulding, and which were designed often to carry out specific functions within the body in which they are implanted.
Such two-dimensional fabrics are for example described in the documents US-C-5 569 273 and 3 124 136.
However, such fabrics have several disadvantages, related to the very structure of the fabric, or to the choice of the base material used for making the threads, or again to the way in which the prosthetic fabric is manufactured. Thus, for example, the known prosthetic fabrics made of synthetic polymer material, are relatively inflexible.
It is also known that the tissual reaction to an implant is the result of a normal process of cicatrizing. Any tissual surgical traumatism is followed by a cascade of physiological events, the principal times of which are as follows:
t0: surgical traumatism, capillary breach;
t0 plus a few minutes: coagulation, fibrin network, release of chemotactic factors;
t0 plus 12 to 48 hours: polynuclear dominant leukocytic afflux;
t0 plus 4 to 8 days: fibroblast afflux
t0 plus 24 hours to 5 days: macrophagic dominant leukocytic afflux;
t0 plus 8 to 21 days: connective differentiation of the cicatrizing reaction;
t0 plus 15 to 180 days: cicatrizing remodelling on contact with the implant.
Even if the exact mechanism are still unknown in certain cases, particularly with regard to the determinism of the intensity of the reaction, it therefore appears that the first 8 days are determinant since they condition the fibroblast afflux.
In non-bony tissue, the equilibrium of the reaction leads to the formation of a fibro-connective membrane which constitutes the interface between the implanted material and the surrounding healthy tissue. Whatever the type of implant, the zone directly affected by a conventional biocompatible material is a minimum of about 50 xcexcm.
Furthermore, in the treatment of parietal inadequacies (principally hernias and eventrations), the prosthetic fabric has the task of providing additional mechanical strength to the surgical reconstruction, and it becomes more effective, and its local tolerance becomes better, as its tissue integration becomes more intimate and more advanced.
The Applicant has established, by its own research, whose results led to the present invention, that several parameters influence the tissual response to a prosthetic implant, namely:
the constituent material of the prosthesis and its possible products of degradation in a biological medium, which must not induce a toxic effect or an effect contrary to the sought effect. In the case of a prosthetic fabric implanted long-term, the aging of the material and its consequences (wear, ejection of components, etc.) are the most difficult factor to predict; only raw materials validated over a long period provide a maximum of safety;
as the organism, so to say, only sees the surface of the material, the properties of the latter assume significant importance. Among all of the surface parameters, the surface energy and the roughness have an important role. In effect, when it is sought to promote cellular adhesion, the surface must be hydrophilic (high surface energy) and smooth in comparison with a cell (of the order of one micron);
only the porosity accessible by the organism is useful with regard to the anchoring of the prosthetic fabric. This porosity in a given volume must be interconnected, and the interconnecting interstices must be sufficient for significant cellular penetration (of the order of 20 to 80 xcexcm approximately), and for tissual differentiation (100 to 300 xcexcm generally constitute a minimum for complete differentiation). It has been recalled above that the minimum distance for setting aside the tissual reaction from the direct influence of the prosthetic material is of the order of 50 xcexcm, which means that for sizes of porosity less than 100 xcexcm, the rehabilitation tissue will be entirely under the influence of the presence of the implant, with little possibility of completed tissual differentiation;
the vascularization and the biomechanical environment of the receiving site condition the intensity of the tissual response. A richly vascularized site (skin, muscles, etc . . . ) will react faster and more intensely than less vascularized tissues (rear chamber of the eye, bone, etc . . . ). Furthermore, the very nature of the receiving site conditions the capacity of regeneration to be identical to that of the wounded tissue. Bone, the connective tissues, mucous membranes, certain parenchymas (the liver for example) can regenerate identically with no significant fibrous scarring. On the other hand, other very specialized tissues (muscles, nerve tissues, etc . . . ) have lost all capacity to regenerate, the cicatrizing of these tissues therefore occurring only by fibrosis;
surgical traumatism constitutes one of the principal factors triggering the previously described cascade reaction. The bigger this is, the more intense the reaction will be and the more pronounced its consequences will be (cicatrizing delay, fibrous sequelae, pain, etc . . . ).
Considering the above, one of the objectives of a good prosthetic fabric is a tissual integration that is as fast as possible, procuring a mechanically satisfactory anchoring without extensive fibrosis, a source of discomfort and pain.
In order to try to achieve this objective, the Applicant has designed, manufactured and marketed, under the name xe2x80x9cPATxe2x80x9d or xe2x80x9cTETxe2x80x9d, a three-dimensional prosthetic fabric, comprising two opposite surfaces, porous or relatively rough, separated from each other by the thickness of the fabric, but linked to each other by binding threads, whose texture depends on the method of obtaining the fabric, for example by weaving and/or knitting.
One such three-dimensional fabric is for example described in the document EP-A-0 621 014, as the central part of a prosthetic assembly furthermore comprising edges formed from a single knitted layer.
In certain cases, the pattern of the prosthetic fabric determines, within its thickness, a plurality of transverse channels or cells substantially parallel to one another, emerging on either side of said fabric on the two porous surfaces respectively, in such a way that it is then possible to speak of an open-worked fabric, allowing direct progress of the repairing cells, starting from each of the surfaces of the fabric.
In the present application, certain terms have the following significance:
xe2x80x9cfabricxe2x80x9d refers to an assembly of threads, obtained in particular by knitting and/or by weaving;
xe2x80x9cporous surfacexe2x80x9d refers to a surface of the fabric which exhibits numerous small orifices, or holes emerging in its surface, thereby conferring upon it a rough appearance.
This type of fabric has widely demonstrated its effectiveness, particularly in terms of the fastest possible integration in the receiving anatomical site, by procuring a mechanically satisfactory anchoring without extensive or significant fibrosis.
The present invention has however sought to improve the tissual integration of a three-dimensional prosthetic fabric such as previously defined, whilst lowering its intrinsic inflammatory power.
According to the present invention, the pattern of the fabric also determines, for each transverse channel or cell, an internal porous wall interconnecting with the adjacent channels.
Preferably, the passage interstices between channels have a width of between 100 and 300 xcexcm.
The porosity of the channel wall is determined in particular by the fabric arrangement of the binding threads, which are themselves made from multifilaments of fibres (for example from polyester) having, by way of example, a diameter of between 10 and 15 xcexcm.
Because of the invention as previously defined, the walls of the channels provide an anchoring zone for the fibrous reaction subject to the implant (the immediate environs of each thread), which nevertheless contributes to a relatively intimate and advanced tissual integration of the prosthetic fabric.
In effect, the Applicant has discovered that with a prosthetic fabric such as previously defined, the three-dimensional structure thus obtained improves cellular recolonization, whilst improving the integration of the fabric, because the available internal volume is increased. Furthermore, when the internal section of each cell or channel is substantially free of any binding thread, the inflammatory reaction of the prosthetic fabric in vivo is particularly reduced.
Furthermore, for an equivalent quantity of material per square metre, a three-dimensional structure such as defined previously makes it possible to open the interior of the fabric more widely than the exterior, which is favorable to a differentiation of a connective tissue histologically normal in the core of the implant. The multidirectional porosity according to the invention furthermore favors the drainage of the site and thus limits the risks associated with collections of liquids (seromas, hematomas, sepsis).
By virtue of the invention, the mechanical properties of the fabric are improved, without increasing the local density of prosthetic material, since the latter is distributed in volume in three directions.
Once the prosthetic fabric is implanted, the cells, present at the center of the volume created by the three-dimensional structure according to the invention, are at least 750 xcexcm from any prosthetic material, if the dimensional conditions defined below are complied with. Thus, the colonizing cells are far from any influence able to delay or disturb the differentiation mechanisms, whilst being less than one millimeter from the receiving tissue, that is to say close to the elements providing the essential elements for a fast rehabilitation (progenitor base cells, blood capillaries, etc . . . ).
These conditions make it possible to obtain a mechanically satisfactory anchoring whilst preserving a thoroughly completed differentiation, such as encountered in a normal connective tissue.
In a preferred embodiment of the invention, each transverse channel emerges on at least one porous surface through an opening of hexagonal shape or through an opening shaped like a water drop. More preferentially, each transverse channel emerges on one porous surface through an opening of hexagonal shape, and on the other porous surface through an opening shaped like a water drop.
Preferentially, the mean diameter of the transverse channels is equal to or greater than 0.3 mm, preferably between 0.7 mm and 2 mm, and more preferably between 1.3 mm and 1.7 mm. In the same way, the transverse channels generally exhibit a length of between about 0.5 mm and 3 mm, and preferably between 1.6 mm and 2.1 mm, corresponding to the thickness of the fabric.
Preferably, the thickness of the fabric is at most equal to 3 mm, and more preferably between 1.7 mm and 2.5 mm.
The binding threads preferably each consist of a plurality of continuous filaments made of a biocompatible material, for example polyester. More preferably still, the fabric comprises two layers of knitted warp threads, determining on the outside the two porous surfaces, linked to each other, and preferably two layers of threads for intermediate binding.
In another preferred embodiment of the prosthetic fabric according to the invention, each transverse channel emerges on at least one porous surface through an opening of macropore type, whose diameter is between 0.7 mm and 2 mm, and more preferably between 1.3 mm and 1.7 mm.
Another subject of the present invention is a parietal and/or visceral prosthesis, obtained with a fabric such as defined previously.
Yet another subject of the present invention is the use of a fabric, according to the invention such as defined, in order to obtain a prosthetic product for surgical use, particularly for manufacturing a parietal and/or visceral prosthesis.
Preferably, the passage interstices between channels have a width of between 100 and 300 xcexcm.